JP2000137039A - Acceleration detector for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a detection error for acceleration by correcting a detection output of an acceleration detecting means according to a result of a varying direction detecting means for increase and decrease of a rotational speed. SOLUTION: An acceleration sensor 1 outputs a voltage proportional to acceleration in a longitudinal direction of a vehicle to be A/D-converted by an A/D converter 2, and outputs an acceleration detection data DA. A magnetic sensor 5 outputs a voltage proportional to magnetic intensity of magnetism magnetized in a tire of a wheel 4 to be A/D-converted by an A/D converter 6, and outputs a magnetism detection data DM. A microcomputer 3A reads the data DA, and averages them in every fixed period H to find average acceleration <A>. In parallel, the computor 3A reads the data DM to search three consecutive upper side peaks P1, P2, P3 from the last consecutive data DM, measures a time T1 between the P1-P2 and a time T2 between P2-P3, determines relative size relating to the T1 and the T2 to detect a direction of increasing and decreasing variation in a rotational speed of a wheel, and corrects the average acceleration to be zero so as to calculate a vehicular speed, when the increasing and decreasing change in the rotational speed of the wheel is not observed even in the case where the <A> is (+).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle acceleration detecting device, and more particularly, to a vehicle acceleration detecting device suitable for calculating a vehicle speed or a moving distance by a vehicle-mounted navigation device or the like.

[0002]

BACKGROUND OF THE INVENTION vehicle navigation apparatus, in order to calculate the movement distance of the vehicle from one point O ₀ in autonomous navigation, an acceleration sensor for detecting a longitudinal acceleration of the vehicle. The vehicle speed v can be obtained by integrating the acceleration α detected by the acceleration sensor once at time t (the initial values of the acceleration and the vehicle speed are the acceleration α ₀ at the point O ₀ , the vehicle speed v ₀ , and the vehicle is stopped. If v ₀ = 0,
α ₀ = 0), and the moving distance R can be obtained by integrating the vehicle speed once at time t (the initial value R of the moving distance).
₀ = 0).

FIG. 11 is a configuration diagram of a vehicle speed detection system of a conventional vehicle-mounted navigation device. 1 is an acceleration sensor that is installed at a predetermined location of the vehicle and detects an acceleration in the front-rear direction and outputs an analog detection voltage that changes in proportion to the acceleration. 2 is an acceleration sensor that outputs an output of the acceleration sensor 1 at a predetermined sampling frequency. A / D which converts / D and outputs acceleration data DA
The D converter 3 is a microcomputer that reads the output of the A / D converter and performs predetermined arithmetic processing. The D converter 3 integrates acceleration data DA output from the A / D converter with time and changes every moment. The vehicle speed v is calculated in real time.

[0004]

When the vehicle is traveling on a flat road at a constant speed, the acceleration sensor 1
Is zero, the vehicle speed gradually increases when accelerating on a flat road, the acceleration α becomes +,
When decelerating on a flat road, the vehicle speed gradually decreases and the acceleration α
Becomes-(see FIG. 12). However, if the speed is not changed when the vehicle goes uphill from a flat road, the acceleration α should be zero, but as shown in FIG. of the vehicle it will sense the longitudinal direction component g _S, thereby outputting an acceleration of +. For this reason, there is a problem that the vehicle speed calculated by the microcomputer 3 becomes higher than the actual speed. Conversely, if the vehicle does not change speed when entering a downhill from a flat road, the acceleration α should normally be zero, but the acceleration sensor 1 determines the longitudinal component of the gravitational acceleration. It senses and outputs a negative acceleration.
For this reason, there is a problem that the vehicle speed calculated by the microcomputer 3 becomes smaller than the actual speed. The present invention has been made in view of the above-described problems of the related art, and has as its object to provide an acceleration detection device for a vehicle that can reduce an acceleration detection error.

[0005]

According to a first aspect of the present invention, there is provided an acceleration detecting device for a vehicle, comprising: an acceleration detecting means for detecting an acceleration of the vehicle; It is characterized by comprising a change direction detecting means and a correction means for correcting the detection output of the acceleration detecting means in accordance with the detection result of the rotational speed increase / decrease change direction detecting means. According to this acceleration detecting device, when the speed does not change when the vehicle goes uphill from a flat road, the acceleration detecting means detects a positive acceleration, but the rotational speed increase / decrease change direction detecting means detects Since the rotation speed does not detect any of the increasing direction and the decreasing direction, the correcting unit corrects the detection output of the acceleration detecting unit to zero. Similarly, if the speed does not change when the vehicle enters a downhill from a flat road, the acceleration detecting means detects a negative acceleration, but the rotational speed increase / decrease direction detecting means increases / decreases the rotational speed of the wheels. And the decrease change is not detected.
The detection output of the acceleration detecting means is corrected to zero. Thus, the acceleration detection error can be reduced. When the vehicle accelerates on an uphill, the rotation speed increase / decrease change direction detecting means detects that the rotation speed of the wheel has increased and changed, and if the detection output of the acceleration detection means indicates + acceleration, If a negative acceleration is output without correction, it may be corrected to zero or a certain positive acceleration. In addition, because the vehicle decelerates on the uphill, the rotation speed increase / decrease change direction detection unit detects that the rotation speed of the wheel has decreased and changed.If the detection output of the acceleration detection unit indicates a negative acceleration, If a positive acceleration is output without performing the correction, the acceleration may be corrected to zero or a certain negative acceleration. In the vehicle acceleration detecting device according to claim 2 of the present invention, the rotational speed increase / decrease change detecting means is provided near the wheel of the vehicle, and the magnetic detecting means detects the magnetism of the wheel in a non-contact manner. It is characterized by including a measuring means for measuring the cycle of the detection output change, and a judging means for judging the direction of increase or decrease in the rotational speed of the wheel based on the measurement result of the measuring means. This makes it possible to detect a change in the rotation speed of the wheel with a relatively simple configuration without wiring for separately taking out the wheel speed signal from the vehicle side.

[0006]

Next, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of a vehicle speed detection system of an in-vehicle navigation device according to the present invention. The same components as those in FIG. 11 are denoted by the same reference numerals. An acceleration sensor 1 is provided at a predetermined location of the vehicle and detects an acceleration in the front-rear direction and outputs a detection voltage proportional to the acceleration. A 2 converts the detection voltage of the acceleration sensor 1 into a digital signal at a predetermined sampling frequency. , Acceleration data D
An A / D converter 4 for outputting A is a wheel of the vehicle, and usually a steel radial tire is used. Reference numeral 5 denotes a magnetic sensor that is installed close to the wheel 4 and detects a magnetic intensity magnetized on the wheel 4 and outputs a detection voltage proportional to the magnetic intensity. Reference numeral 6 denotes a detection voltage of the magnetic sensor 5. This is an A / D converter that performs A / D conversion at a predetermined sampling frequency and outputs magnetic detection data DM. Normally, when a steel radial tire is used for the wheel 4, the detection voltage of the magnetic sensor 5 periodically changes as the wheel 4 rotates as shown in FIG. 2 because the tire is naturally magnetized. A period T required for one rotation of the time interval of the wheel 4 Figure two upper peak P ₁ adjacent the second waveform, P _2, rotational speed ω 2
π / T (rad / s).

Reference numeral 3A denotes a microcomputer which reads the acceleration data DA output from the A / D converter 2 and calculates the vehicle speed by time integration. The microcomputer 3A detects the direction of increase or decrease in the rotation speed of the wheel 4 based on the magnetic detection data DM output from the A / D converter 6, corrects the acceleration data DA based on the detection result, and calculates the vehicle speed. . Specifically, a change cycle of the magnetic detection data DM is measured, and a change direction of the rotation speed of the wheel is determined by determining a change direction of the measured cycle.

Next, the operation of this embodiment will be described with reference to FIGS. 3 and 4 are flowcharts showing a vehicle speed calculation process by the microcomputer 3A.
9 are explanatory diagrams of the acceleration correcting operation, and FIG.
FIG. 6 is a diagram showing a change in the magnetic strength detected by the magnetic sensor 5 and the acceleration detected by the acceleration sensor 1 during acceleration traveling on a flat road. FIG. FIG. 7 is a diagram showing a change in the detected magnetic intensity and the acceleration detected by the acceleration sensor 1. FIG. 7 shows the magnetic intensity detected by the magnetic sensor 5 and the detection by the acceleration sensor 1 while traveling on a flat road at a constant speed. FIG. 8 is a diagram showing a change in acceleration, FIG. 8 is a diagram showing a change in the magnetic strength detected by the magnetic sensor 5 and the change in acceleration detected by the acceleration sensor 1 while traveling uphill at a constant speed, and FIG. FIG. 7 is a diagram illustrating a state of a change in a magnetic strength detected by a magnetic sensor and a change in acceleration detected by an acceleration sensor during traveling at a constant speed on a downhill. A / D
The converter 2 outputs n pieces of acceleration data DA during a certain vehicle speed calculation period H, and the A / D converter 6 outputs m pieces of magnetic detection data DM. For example, H = 1 sec, n = 20, and m = 200.

First, the microcomputer 3A starts processing when the engine is stopped, and sets ₀ as an initial value v ₀ of the vehicle speed v in a built-in memory (not shown). Further, zero is set in the internal memory as the number i of vehicle speed calculations (step S1 in FIG. 3). Then, the acceleration data DA newly output from the A / D converter 2 and the magnetic detection data DR newly output from the A / D converter 6 are read and stored in the built-in memory (step S2). The built-in memory can store the latest n pieces of acceleration data DA and the latest mk pieces of magnetic detection data DR (k is, for example, 10). DR and DA are written in the built-in memory so as to leave the latest data. The microcomputer 3A checks whether new n data not yet used for the calculation of the vehicle speed has been stored in the built-in memory (step S3). If NO, the process returns to step S2. Then when it becomes YES in step S3, increments i (step S4), and calculates the acceleration <A _1> obtained by averaging the last n acceleration data DA (step S5).

Subsequently, the latest series of magnetic detection data DR
, Based on the last three consecutive upper peaks P ₁ ,
Find P _2, P ₃ (step S6). Whether the vehicle when there is no left stopped state, since immediately after the start traveling not turning wheels 4 3 or more revolutions, NO is determined in step S7, it is corrected acceleration <A _1> obtained above <A ₁ >
'And (step S8), and the correction acceleration <A _1>' from the initial value v ₀ Prefecture, the speed v ₁ at time _{t 1, v 1 = v 0} + <A 1>' of · H in formula It is obtained and output (steps S9 and S10).

Then, returning to step S2, the acceleration data DA newly output from the A / D converter 2 and the magnetic detection data DR newly output from the A / D converter 6 are read and stored in the built-in memory. . It is checked whether new n data not yet used for the calculation of the vehicle speed has been stored in the built-in memory (step S3). If NO, the process returns to step S2. Thereafter, it elapses H time from calculating the previous vehicle speed, when it becomes YES in step S3, to calculate the n number average acceleration <A _2> (step S4, S
5).

Subsequently, the latest series of magnetic detection data DR
Based on the last three consecutive upper peaks. Proceeds to step S8 and determines NO in step S7 when not yet exist, 'and, the corrected acceleration <A _2>' the <A _2> obtained this time as the compensated acceleration <A _2> and the previous vehicle speed v ₁ and from the speed v ₂ at time _{t 2, v 2 = v 1} + <A 2>'· H calculated by calculated outputs of the (step S9, S10). Hereinafter, the same processing is repeated.

Thereafter, at a certain time t _i , step S
3 is YES, and the acceleration data <A _i that n number average>
Is calculated (steps S4 and S5), and in step S6, when the latest three consecutive upper peaks P ₁ , P ₂ and P ₃ are searched based on the latest series of magnetic detection data DR, they are present. when it becomes YES in step S7 have, (corresponding to a period in which the wheel rotates 1) two time peaks between P ₁ -P ₂ before the three T ₁ and between the two peaks after P
₂ -P ₃ times T ₂ to measure the (wheel corresponds to the period of one rotation) (step S11). Then, the level decision of T ₁ and T _2. T _1> if T ₂ is determined to increase or decrease the change direction of the wheel rotation speed of a increasing direction (YES in step S20 in FIG. 4), the current acceleration <A _i> is + or 0
If it is the correct acceleration <A _i> '(step S21, S22), <A _i> is - corrected acceleration if <
A _i > ′ is set to 0 (step S23).

On the other hand, if T ₁ <T ₂ , it is determined that the direction of increase or decrease in the rotational speed of the wheel is the decreasing direction (step S).
24), the current acceleration <A _i> is - or as if 0 as the correction acceleration <A _i> '(step S25, S
26), <A _i> is the zero correction acceleration <A _i> 'if + (step S27). Also, if T ₁ = T _2, determines that decrease no change in the rotational speed of the wheel (both NO in step S20 and S24), the correction acceleration <A _i> '
Is set to 0 (step S28). Then, the process proceeds to step S9 of FIG. 3, the compensated acceleration <A _i> 'and the previous vehicle speed v
from _i-1 Tokyo, the vehicle speed v _i at time _{t i, v i = v i} -1 + <A i>'· H calculated by calculated outputs of (step S10).

For example, when the vehicle is accelerating on a flat road, the acceleration detected by the acceleration sensor 1 becomes + (see the lower side of FIG. 5).
D converter 2 outputs data acceleration <A _i> obtained by averaging the n partial to a +. The change period of the magnetic intensity detected by the magnetic sensor 5 gradually decreases (see the upper side of FIG. 5),
Of the latest three consecutive upper peaks P ₁ , P ₂ , and P ₃ found in step S 6, the period T ₁ between the preceding two upper peaks P _{1 and} P ₂ and the rear two upper peaks P
When the period T ₂ of the between ₂ -P ₃ to the level decision then measured in step S11, becomes YES in step S20 in FIG. 4, since the change in increase and decrease direction of the rotational speeds of the wheels 4 is increased direction, in the processing of step S22 acceleration <A _i> is directly with the corrected acceleration <A _i> '.

On the other hand, when the vehicle is decelerating on a flat road, the acceleration detected by the acceleration sensor 1 becomes-(see the lower side of FIG. 6), and A / A is determined in step S5 of FIG.
The output data of the D converter 2 acceleration <A _i> is obtained by averaging the n partial - to become. The change period of the magnetic intensity detected by the magnetic sensor 5 gradually increases (see the upper part of FIG. 6).
Of the latest three consecutive upper peaks P ₁ , P ₂ , and P ₃ found in step S 6, the period T ₁ between the preceding two upper peaks P _{1 and} P ₂ and the rear two upper peaks P
When the period T ₂ of the between ₂ -P ₃ to the level decision then measured in step S11, YES next at the step S24 in FIG. 4, since the change in increase and decrease direction of the rotational speeds of the wheels 4 is the decreasing direction, in the processing of step S26 acceleration <A _i> is directly with the corrected acceleration <A _i> '.

Further, the vehicle travels on a flat road at a constant speed.
The acceleration detected by the acceleration sensor 1 is zero.
(See the lower side of FIG. 7), and in step S5 of FIG.
Of the output data of the A / D converter 2 for n data
Acceleration <A_i> Becomes 0. Detected by magnetic sensor 5
The change period of the magnetic intensity is constant (see the upper part of FIG. 7).
), The three most recent adjacent runs found in step S6.
Continued upper peak P₁, P _Two, P_ThreeOf the two upper front
Peak P₁-P_TwoPeriod T between₁And the two upper pins
Ark P_Two-P_ThreePeriod T between_TwoIs measured in step S11.
After that, when the size is determined, steps S20 and S24 in FIG.
And both become NO, and the direction of increase / decrease of the rotation speed of the wheel 4
Does not change, the corrected acceleration <A_i> 'Is 0
(Step S28). In this way, the vehicle is on a flat road
When traveling on a road, the output of the acceleration sensor 1 has an error.
And average the output data of the A / D converter 2 for n data
Accelerated <A _i> The same corrected acceleration <A_i> 'Tosa
To obtain the correct vehicle speed by using it to calculate the vehicle speed.
Can be

On the other hand, when the vehicle is traveling uphill at a constant speed, an error due to the gravitational acceleration occurs in the output of the acceleration sensor 1, so that the acceleration detected by the acceleration sensor 1 becomes + (see the lower part of FIG. 8). see side), the acceleration <A _i> of obtaining the output data of the a / D converter 2 and the average of n partial in step S5 becomes +, it becomes earlier than the actual When used as it is in the vehicle speed calculation. At this time, the change period of the magnetic intensity detected by the magnetic sensor 5 is constant (see the upper side of FIG. 8), and the three latest adjacent upper peaks P ₁ , P ₂ , of P _3, before the period T ₁ of the between two upper peak P ₁ -P _2, when the period T ₂ of the between rear two upper peak P ₂ -P ₃ to the level decision then measured in step S11, FIG. 4 are NO in both steps S20 and S24, and there is no change in the direction of increase or decrease in the rotational speed of the wheel 4, so that the corrected acceleration <
A _i> 'is correctly 0 (step S28), the correction acceleration <A _i>' can obtain a correct vehicle speed by the calculation of vehicle speed.

Conversely, when the vehicle travels downhill at a constant speed,
The acceleration sensor 1 outputs
Since an error occurs, the acceleration detected by the acceleration sensor 1 is
-(See the lower side of FIG. 9), and in step S5, A
Acceleration obtained by averaging n output data of the / D converter 2
Degree <A_i> Becomes-and is used for calculation of vehicle speed
And it will be slower than it really is. At this time, the magnetic sensor 5
The period of change of the magnetic intensity detected at the time is constant (FIG. 9).
), The latest adjacent one found in step S6.
Three consecutive upper peaks P₁, P_Two, P_ThreeOf the previous two
Two upper peaks P₁-P_TwoPeriod T between₁And the back two
Upper peak P of_Two-P_ThreePeriod T between_TwoTo step S11
When the size is determined after the measurement in step S20, the process proceeds to step S20 in FIG.
And S24 are both NO, and increase / decrease of the rotation speed of the wheel 4
Since the direction of change does not change, the corrected acceleration <A_i> '
Is correctly set to 0 (step S28), and the corrected acceleration <
A _i> 'To calculate the vehicle speed to obtain the correct vehicle speed
Can be.

When the vehicle is traveling while decelerating on an uphill, an error due to the gravitational acceleration occurs in the output of the acceleration sensor 1. Therefore, in step S5, the output data of the A / D converter 2 is averaged for n data. to seek acceleration <A _i>
Can be any of +,-, and 0, but the step S in FIG.
24 In YES, since change in increase and decrease direction of the rotational speed of the wheel is decreasing direction, <A _i> is - while the intact are corrected acceleration <A _i> 'If 0 (step S2
6), <A _i> is + errors are corrected acceleration <A _i> 'is 0 at step S27 is smaller when the suppression of the vehicle speed error is achieved. Conversely, even when the vehicle is traveling while accelerating on a downhill, an error due to the gravitational acceleration occurs in the output of the acceleration sensor 1.
/ D converter 2 outputs data of n partial average seek acceleration <A _i> is +, -, but can become any of 0, step S20 in YES next to Figure 4, increasing or decreasing the rotational speed of the wheel the change direction is the increasing direction, while it is the corrected acceleration <A _i> 'when <A _i> is + and 0 (step S22), <A _i> is - step S23 when
In the compensated acceleration <A _i> 'is 0 and has been an error is small, suppression of the vehicle speed error is achieved. Note that the microcomputer 3A executes the processing of FIGS. 3 and 4 at high speed.
The data output from the A / D converter 2 and the A / D converter 6 are read without omission by the processing in step S2.

According to this embodiment, while the vehicle is running,
Since the detection output of the magnetic sensor 1 changes periodically, the microcomputer 3A detects the latest three adjacent upper peaks based on the output data of the A / D converter 6,
Of these, the time T ₁ between the two upper peaks before and the time T ₂ between the two upper peaks after are measured, and the direction of change in the length of the measured time (corresponding to the rotation cycle) is determined. The direction in which the rotational speed of the wheel 4 is increased or decreased is determined. When the speed does not change when the vehicle enters an uphill (downhill) from a flat road, the acceleration sensor 1 detects + (−) acceleration, and the microcomputer 3 outputs the output of the A / D converter 2. data n number average seek acceleration <A _i> is + (-) and becomes to cause, but since the change in increase and decrease direction of the rotational speeds of the wheels 4 is no increase or decrease, the correction acceleration <A _i> '=
The vehicle speed is calculated by correcting it to zero. As a result, a vehicle speed without error can be obtained.

When the vehicle is traveling on a flat road at a constant speed, the acceleration sensor 1 detects zero acceleration, and the microcomputer 3 averages n output data of the A / D converter 2 to obtain the average. acceleration <A _i> but becomes 0, since the change in increase and decrease direction of the rotational speeds of the wheels 4 is no increase or decrease, as 0 a correction acceleration <A _i> ', correctly calculate the vehicle speed,
When the vehicle is accelerating (decelerating) on a flat road, the acceleration sensor 1 detects an acceleration of + (−), and the A / D converter 2
Output data of n partial average seek acceleration <A _i> is a + (-) and becomes, since change in increase and decrease direction of the rotational speeds of the wheels is increasing direction (decreasing direction), the acceleration <A _i> it is possible to correctly calculate the vehicle speed as the intact correction acceleration <A _i> '.

Further, when the vehicle is traveling while decelerating on an uphill, an error due to the gravitational acceleration occurs in the output of the acceleration sensor 1, so that the acceleration detected by the acceleration sensor 1 is any of +, 0, and-. Become a microcomputer 3
Acceleration A is calculated by averaging the n partial output data of the A / D converter 2 <A _i> is +, -, but can become any of 0,
Since the direction of increase / decrease in the rotation speed of the wheels is the decreasing direction,
The microcomputer 3A is <A _i> is - a 'while the correction acceleration <A _i> When <A _i> is +' as corrected acceleration <A _i> If 0 suppression of vehicle speed error as the 0 Can be. Conversely, even when the vehicle is traveling while accelerating on a downhill, an error due to gravitational acceleration occurs in the output of the acceleration sensor 1, so that the acceleration detected by the acceleration sensor 1 is any of +, 0, and-. , The microcomputer 3A outputs the output data of the A / D converter 2 to n
Pieces minute average seek acceleration <A _i> is +, -, but can become any of 0, since the change in increase and decrease direction of the rotational speeds of the wheels is increasing direction, when <A _i> is + and 0 the 'while the, <A _i> is - the correction acceleration <A _i> when' it corrected acceleration <A _i> to reduce the error as 0, it is possible to suppress the vehicle speed error.

Further, the magnetic sensor 5 disposed close to the wheel 4 detects the magnetism of the tire of the wheel 4 which is naturally magnetized. By measuring the cycle and determining the change in the length of the cycle, the direction of increase or decrease in the rotation speed of the wheel 4 is determined, so that a relatively simple configuration is sufficient.

When the vehicle is traveling while decelerating on an uphill, an error due to the gravitational acceleration occurs in the output of the acceleration sensor 1. Therefore, the acceleration detected by the acceleration sensor 1 is any of +, 0, and-. Become a microcomputer 3
Acceleration A is calculated by averaging the n partial output data of the A / D converter 2 <A _i> is +, -, but can become any of 0,
Since the direction of increase / decrease in the rotation speed of the wheels is the decreasing direction,
The microcomputer 3A is <A _i> is - 'while the, <A _i> 0 and + correction acceleration <A _i> When the' as corrected acceleration <A _i> when a certain constant negative value By doing so, the vehicle speed error may be suppressed. Conversely, when the vehicle is traveling while accelerating downhill,
Since an error due to the gravitational acceleration occurs in the output of the acceleration sensor 1, the acceleration detected by the acceleration sensor 1 becomes any of +, 0, and-, and the microcomputer 3A outputs the output data of the A / D converter 2 for n data. Average acceleration <A
_i> is +, -, can become any of 0, but since change in increase and decrease direction of the rotational speeds of the wheels is increasing direction, <A _i> is +
While it is the correction acceleration <A _i> 'is when, <
A _i> 0 and - may be the suppression of the vehicle speed error by the correction acceleration <A _i> 'positive constant value one when the.

Also, in step S6 of FIG.
Thus, the latest j (j is an integer of 4 or more) consecutive
Side peak P₁, P_Two, P_Three, ..., P_jTo look for
When it exists, in step S11, P₁-P_Twowhile
Time T₁, P_Two-P_ThreeTime T between_Two, ..., P_j-1−
P_jTime T between_j-1Is measured, and step S2 is performed.
At 0, T₁> T_TwoInstead of determining whether
₁> T_Two> T_Three・ ・ ＞ T _j-1Whether the relationship of
Or T₁+ T_Two+ ... T_j-2> T _Two+ T
_Three+ ... T_j-1To determine if the relationship
If YES, it is determined that the rotation speed is increasing and changing.
Then, the process proceeds to step S21, and step S24
Then T₁<T_TwoInstead of determining₁<T_Two<T
_Three.. <T _j-1Judge whether the relationship of
Well, T₁+ T_Two+ ... T_j-2<T _Two+ T_Three+ ... T
_j-1Is determined whether or not the relationship is established, and YES
In the case of, it is determined that the rotation speed is decreasing and
To step S25, and in the case of NO, the rotation speed
It is determined that there is no increase / decrease change and the process proceeds to step S28.
In this case, the direction of increase or decrease of the rotational speed may be changed.
Can be determined.

The rotation period (equivalent to the rotation speed) of the wheel is detected by detecting the intensity of magnetism applied to the tire of the wheel by a magnetic sensor and measuring the period of the change in the detected magnetic intensity. However, a reflective seal is attached to a tire of the wheel or one place of the wheel, and an optical rotation detector including a light emitting element and a light receiving element is installed in a place in the vehicle body, in proximity to the reflective seal and opposed to the reflective seal, The light emitted from the light emitting element is reflected by the reflection seal so that the reflected light can be detected by the light receiving element, and the rotation cycle of the wheel is detected by measuring the change cycle of the light receiving element output of the light rotation detector. You may do it.

[0028]

According to the present invention, there is provided rotation speed increase / decrease change direction detecting means for detecting the direction of increase / decrease change of the rotation speed of the wheel, and the detection output of the acceleration detection means is detected by the rotation speed increase / decrease change direction detection means. Since the correction is performed according to the result, the detection error of the acceleration can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a vehicle speed detection system of a vehicle-mounted navigation device according to one embodiment of the present invention.

FIG. 2 is a diagram showing a state of a change in magnetic strength detected by a magnetic sensor during traveling.

FIG. 3 is a flowchart illustrating a vehicle speed calculation process by the microcomputer in FIG. 1;

FIG. 4 is a flowchart showing vehicle speed calculation processing by the microcomputer in FIG. 1;

FIG. 5 is a diagram showing a state of a change in a magnetic strength detected by a magnetic sensor and a change in acceleration detected by an acceleration sensor during acceleration traveling on a flat road.

FIG. 6 is a diagram showing a state of a change in a magnetic strength detected by a magnetic sensor and an acceleration detected by an acceleration sensor during deceleration traveling on a flat road.

FIG. 7 is a diagram showing a state of a change in a magnetic strength detected by a magnetic sensor and a change in acceleration detected by an acceleration sensor while traveling at a constant speed on a flat road.

FIG. 8 is a diagram showing a change in the magnetic strength detected by the magnetic sensor and the change in acceleration detected by the acceleration sensor during traveling at a constant speed on an uphill.

FIG. 9 is a diagram showing a change in the magnetic strength detected by the magnetic sensor and the change in acceleration detected by the acceleration sensor while traveling downhill at a constant speed.

FIG. 10 is a diagram illustrating an acceleration correction operation according to a modification of the present invention.

FIG. 11 is a block diagram showing a configuration of a vehicle speed detection system of a conventional vehicle-mounted navigation device.

FIG. 12 is a diagram showing a relationship between acceleration detected by an acceleration sensor and a vehicle speed when traveling on a flat road with changing speed.

FIG. 13 is a diagram showing a relationship between acceleration detected by an acceleration sensor and a vehicle speed when traveling uphill at a constant speed.

[Explanation of symbols]

Reference Signs List 1 angular velocity sensor 3A microcomputer 4 wheel 5 magnetic sensor

Claims (2)

[Claims] 1. An acceleration detecting means for detecting an acceleration of a vehicle, a rotational speed increasing / decreasing direction detecting means for detecting a direction of an increasing / decreasing change in a rotational speed of a wheel, and a detection output of the acceleration detecting means, a rotational speed increasing / decreasing direction. A vehicle acceleration detection device, comprising: a correction unit that corrects according to a detection result of a detection unit. 2. The rotation speed increase / decrease change direction detection means is provided near a wheel of a vehicle, and detects a magnetism of the wheel in a non-contact manner, and measures a period of a change in detection output of the magnetism detection means. The vehicle acceleration detection device according to claim 1, further comprising: a measurement unit; and a determination unit configured to determine a direction in which the rotational speed of the wheel increases or decreases based on a measurement result of the measurement unit.